My Question is why I can't speak right English when sometime I write very right english
You are not able to speak correct english because your english grammar fundamentals are weak. Just open a good grammar boom and brush up your basic grammar topics like tenses, articles, prepositions and speech. Then start reading newspapers or books in english so that you understand the correct way of speaking. Finally keep thinking in English and speaking english as much as possible. I think this should help you improve your English.